Quantum cascade lasers provide a tunable mid-infrared (MIR) light source that can be used for spectroscopic measurements and images. Many chemical components of interest have molecular vibrations that are excited in the MIR region of the optical spectrum, which spans wavelengths between 5 to 25 microns. Hence, measuring the absorption of MIR light at various locations on a sample can provide useful information about the chemistry of the sample as a function of position on the sample.
One class of imaging spectrometers measures the light reflected from the sample as a function of position on the sample and wavelength of the illuminating MIR light. In many samples of interest, the range of reflectivities observed across the sample presents challenges as the dynamic range of the detectors is insufficient to measure the reflected light with sufficient accuracy.